In the message the corporation said it was aware of the ongoing trouble and was working to fix it so sites, services and pages were reachable again.

At midday it released another statement saying that the BBC website was now “operating normally”.

“We apologise for any inconvenience you may have experienced,” it said.

The BBC has yet to confirm or deny that such an attack was responsible for the problems.

A group that says it targets online activity linked to so-called Islamic State (IS) has claimed it was behind an attack on the BBC’s website.

All the BBC’s websites were unavailable for several hours on New Year’s Eve after what a BBC source described as a “distributed denial of service” attack.

The group, calling itself New World Hacking, said it had carried out the attack as a “test of its capabilities”.

A “distributed denial of service” attack, which the group claims it carried out, aims to knock a site offline by swamping it with more traffic than it can handle.

In a tweet to BBC technology correspondent Rory Cellan-Jones, the group said: “We are based in the US, but we strive to take down Isis [IS] affiliated websites, also Isis members.

Ownz said his group used a tool called Bangstresser – created by another US-based “hacktivist” – to direct a flood of traffic against the BBC, and had supplemented the attack with requests from its own personal computer servers.

The group has already used the technique against IS websites, but intended to “really get into the action” against a new list of targets associated with the militant Islamist group from Tuesday, Ownz claimed.